Land mine exploder device



' Aug. 5, 1947- A. R. WILLIAMS LAND MINE EXPLODER DEVICE Filed Jan. 21, 1944 s She'etis-Shee t 2 ALusnN RNVILLIAMS,

Aug. 5, 1947. A. R. WlLLlAMS 2,425,018

LAND MINE EXPLQDER' DEVICE Filed Jan. '21, 1944 s Sheets-Sheet s 'I'IIH'I II I l Patentecl Aug. 5, 19 4? UNETE STATES PTENT QFFEC (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 6 Claims.

1 The invention described herein may be manufactured and used by or for the Government for governmental purposes Without the payment to me of any royalty thereon.

This invention relates to a method of and apparatus for applying pressure either to the earths surface or to any fiat or approximately fiat surface at a plurality of points progressively, according to a prearranged pattern. More particularly, the invention provides for the pressure application by impact and sustained effort by relatively simple and light apparatus capable of exerting extremely heavy pressure.

The invention contemplates numerous applications, for example, earth tamping, breaking up hard sheet material such as sheet concrete and thick ice, surface exploration, militar mine field clearing and the like, especially where the application makes impact and sustained pressure desirable.

Apparatus according to the present invention is capable of readily exerting pressures even as much as several thousand pounds per square inch using relatively simple and light apparatus. Since the impact force increases as the square of the velocity, and the area of impact may be reduced by employing a pointed case hardened compacter element, the mechanism may, by proper coordination of these two factors, be caused to exert tremendously high compacting stresses.

The apparatus herein contemplated is simple and compact, is readily transported, and lends itself readily to breaking the concrete into small, and easily handled pieces. The machine may, moreover, be designed to produce sections of any desired size.

The breaking of thick sheet ice on bodies of navigable water to provide for navigation under severe winter conditions also presents a difiicult problem. Special ice-breaking vessels are used for this purpose as vessels of ordinary construction are not suitable. Apparatus of the present invention can be readily adapted to use in ice breaking without special propelling equipment and can, therefore, be attached to and be driven by any vessel, thus making each vessel capable of functioning as its own ice breaker.

It is well recognized that the planting of extensive mine fields serves an important tactical function in denying the use of strategic areas such as airports and highway facilities to a pursuing force. Many expedients have been tried in attempts to locate and destroy, remove, or other- Wise render ineffective such mine fields. When location and removal are attempted manually,

enemy action and the presence of occasional booby traps, and anti-personnel mines expose the removing and locating personnel to great danger. Most of the machines which have been tried in efi'orts to explode the mines without exposing personnel have been of such a character that the exploding device was itself destroyed or seriously damaged by any exploded mines. Certain other of the mechanical arrangements employed have raised such clouds of dust as to cause serious difficulty with engine air cleaners and to necessitate buttoning up the tank or other propelling vehicle and driving in accordance with directions given by radio. Other devices which have been employed have caused such disturbance of the ground surface as to require consolidation of the ground before it could be again used as an airport, for example, and some have had the bad habit of throwing exploding mines onto or under the vehicle propelling the mine exploding device.

The extension use which is made of land mines in modern warfare makes it essential that some effective means be developed which is capable of destroying the mines in place Without being itself destroyed, and which operates with a minimum of disturbance to the surface of the ground.

Having the factors above mentioned in mind, it is one of the purposes of this invention to provide a compacting device capable of adaptation to any of the above uses and capable, when it is employed as a mine exploding device, of functioning effectively, and of absorbing the shocks of repeated mine explosions without significant damage to the equipment.

It is a further object of this invention to provide a mine exploding device which can be operated with a minimum input of energy, which will leave the surface of the ground in which there are no mines in condition for immediate reuse, and which will cause a minimum of disturbance in the ground adjacent an exploded mine.

It will be obvious to those familiar with the nature of explosive reactions that a minimum disturbance of the surrounding ground surface will take place when a mine is detonated without much confinement. An ideal condition would be one in which the mine could be detonated in place confined only by the shallow covering of earth above it. In such a case, the force of the explosion would be dissipated harmlessly in a substantially vertical direction.

Such an ideal condition would be closely approximated by causing the end of a stafllike hammer member to impinge upon the mine with sufiicient force to cause explosion thereof. In the case of such a body having a diameter small in relation to its length and Weight, the requisite force could be applied without substantial confinement of the explosion, and with a relatively small amount of kinetic energy being imparted to it.

In a practical embodiment of such a device, there may be provided a plurality of hammers provided with elongated heads for impingement upon the ground, and operatively connected to a propelling vehicle in spaced relation to each other. Such hammers may be operated to cause the heads to reciprocate in a substantially vertical direction, and if the assembly is moved forwardly at a rate properly coordinated with the rate of reciprocation, the heads may be caused to impinge upon the ground at spaced intervals in accordance with a predetermined pattern. Proper choice of the physical constants of such an arrangement can be made to produce a pattern of points of impact so closely spaced across the path of movement, and along the same, as to compact a substantial portion of the area traversed, and where the device is employed for mine clearing to make it impossible for any pressure sensitive mine in the area covered to fail to be activated. Such a construction will present a minimum of projected area to the blast and suitable means may be provided to allow the hammer to yield with the blast or to absorb the energy received therefrom either as internal stress or with other energy-absorbing means, such as hydro-spring or hydro-pneumatic recoil mechanism.

Experimental determinations have supported a conclusion that if, in using the device for mine field clearing, the projected area of the hammer be kept at a minimum commensurate with adequate mechanical strength, and the weight applied thereto be increased, a point may be arrived at Where the mass of the hammer will itself be sufficient to absorb the energy of the explosion without imparting appreciable velocity to it. If bodies of lighter weight be used, it has been found that suitable spring or shock absorbing means may be profitably utilized to absorb a part of the energy from the blast without damage.

Experimental work has also proved that a shaft-like member fitted with a foot of relatively hard material and having a length relatively great in relation to its diameter, may have its hardened surface exposed to the explosion of a land mine without significant damage other than a moderate erosive action on the surface exposed directly to the blast.

When the invention is embodied in a mine clearing device, it may be moved over a mined area by an armored vehicle, such as a tank or the like, so as to explode by direct impact any mines which may have been sown in the area to be cleared. It is to be understood that the apparatus can be either pushed or pulled and that manual, as well as mechanical, propulsion is possible. For military uses, it is desirable that the operating personnel be shielded from 'enemy fire, and from the blast of any mines detonated by the device, hence, reference is made to an armored propelling vehicle, but it is to be understood that the illustration made i intended to be exemplary and not limiting in character.

The exact nature of the inventionyas well as other objects and advantages thereof, will be apparent from this description of certain em- 4 bodiments shown in the accompanying drawing in which:

Figure 1 is a side elevation of a single elementary impact member together with actuating means capable of embodiment in devices of the invention;

Figure 2 is a top plan View of the forward portion of a tank having a complete embodiment of my invention mounted thereon and showing one type of impact pattern which may be produced;

Figure 3 is an enlarged top plan partially in section, of a portion of the unit illustrated in Figure 2;

Figure 4 is a side elevational View corresponding to Figure 2;

Figure 5 is a side elevational view of a compacting element, the view illustrating diagrammatically the path followed by one of the compacting elements referred to a plane moving forward at the same velocity as the propelling vehicle and compacter assembly;

Figure 6 is a diagrammatic view illustrating the path followed by the tip of thecompacter element with relation to the ground, as the tank and compacter assembly moves forward;

Figure '7 is a vertical sectional view, partially in elevation, and with parts broken away, of a preferred form of compacter unit in which a hydrospring energy absorbing means is employed;

Figure 8 is a sectional view illustrating a combined hydraulic and pneumatic energy absorbing means capable of use with compacter units embodying the invention;

Figure 9 is a top plan of the energy absorbing device of Figure 8;

Figure 10 is a vertical sectional view of another form of energy absorbing device operating hydropneumatically and capable of use with compacters of the present invention;

Figure 11 is avertical sectional view of a further modified form of compacter element with a pneumatic energy absorbing means, the compacter support and actuating means being also shown; and

Figure 12 is a top plan View of a means for controlling the elevation of a compacter assembly.

The invention will now be described as embodied in a mine field clearing device, not only because the broad concept first arose in connection with tactical problems encountered by an army in the field, but also because itaffords an excellent illustration of the practical aspects of the invention. In its simplest form, the device consists merely of a plurality of impact elements or hammers arranged to be brought successively into forcible contact with the surface of the ground according to a predetermined pattern. The spacing of the points of impact depends not only upon the number and location of the compacting element, but also upon the periodicity of their actuation as determined by the propelling mechanism for the compacter assembly and the arrangement of the actuating mechanism of the individual units.

From the above it follows that by suitably proportioning themass of the compacter elements and the rate at which they are driven so that the energy expended by the impact of a compacter element substantially balances the energy expended by an exploded mine, the upward and downward forces oppose each other and substantially balance. This is an ideal condition in that it reduces the weight of the compacter elements and the supporting mechanism, cuts down gle m the power required to drive the device, and makes it possible to materially reduce damage to the compacter by the exploding of mines beneath it. Under such balanced conditions of operation, the strength of the compacter assembly need be only great enough to withstand the mechanical pounding to which it is subjected as the device traverses rough and stony or uneven terrain. This mechanical pounding may be reduced materially by providing shock absorbing means in the compacter elements or in the mounting means or in both of them.

In this description, several embodiments of the invention will be referred to in order to indicate the broad scope of the concept, but numerous other and equivalent applications will occur to those skilled in the art, and this specification is,

therefore, to be construed as exemplary only.

Figure 1 of the drawing is intended to illustrate the invention in simple elementary, and more or less diagrammatic, form. Here reference character l3 designates a metal compacter element in the form of a hammer streamlined to present a minimum area to an upwardly acting explosive blast, and preferably having its lower end or foot of such hardness and chemical composition as to resist mechanical damage from impact, and erosion from gases liberated by exploded mines.

When the elements are employed for impact only, mechanical damage only need be provided for. The element I3 is supported by an arm Id adapted to rock about a fulcrum I5 moving in slot IS in' the arm, the arm being actuated by an eccentric I? carried by a rotating shaft 18. It will be apparent that as the shaft and eccentric rotate, the element It will execute an up-anddown motion in an approximately vertical line and that by suitable design of the slot, the arm and the eccentric, the element may be arranged to move in any desired path. This arrangement is, therefore, merely a mechanically-driven hammer which may be duplicated to form an assemblysimilar to that shown in Figure 2.

Referring now to Figure 2, reference character is designates a propelling vehicle, here shown as a tank, and having mounted thereon a compacter or exploder device made up oftwo groups of units each receiving power from the tank. As shown in Figure 3, each group has a drive shaft 2| mounted in suitable bearings 22 carried by the body structure of the vehicle. A clutch 23 applies power to the shafts Zl from the forward drive shaft 24 of the tank through suitable gearing indicated generally at 25, it being understood that both shafts 2! are driven similarly.

Eccentrics 26 carried by the shaft 2i actuate short arms 2? and long arms 28, each arm carrying at its outer end a compacter element C secured in place as indicated in Figure l. The eccentrics and the arms which they drive are suitably spaced along the shaft 25 so as to properly relate the points of impact of the various elements C. Each arm carries a bushing 29 slidably mounted on it, each bushing carrying in turn two rocker pivots 3! received in journals 32 in housing 33 surrounding the eccentric mechanism and journaled on the shafts 2i. As shown, two housings 33 are provided, one for each group assembly on each shaft ill, but the arrangement of the housing may be varied to suit convenience. Connected to each housing 33 is an elevating device in the form of a cable 3% attached to it centrally as at 35 and passing over guide pulley 36. By tightening or releasing .the cable, either housing, and the compacter group assembly to which it is attached,

may be elevated t inoperative position or adjusted to a suitable height to meet conditions such as rough terrain, muddy terrain, barbed wire entanglements and the like. Either unit may be adjusted independently of the other, as, for example, when one unit is on lower ground than the other. Also, the number of groups may be increased to provide more flexibility of operation over uneven terrain, the illustration of two groups being merely by way of example.

It will be obvious that as the drive shafts 2d are rotated by the forward drive of the tank or any other suitable vehicle means each of the arms 21 and 28 will swing about an axis extending through the rocker pivots 3! By suitable adjustment of the inclination of housings 33, it will be apparent that during rotation of the shafts 2!, each compacter member may be caused to strike the ground a blow of considerable force, and by proper selection of the speed rates between the forward drive and the shafts, these impacts may be caused to occur at definitely spaced intervals so close to one another as to make it impossible for any pressure sensitive mine in the path to be cleared to be left untouched. The lateral spacing of the oompacter elements will be such as to com plete a checkerboard pattern of impacts as illustrated, or any geometrical pattern, regular or irregular, to effectively cover the area to be traversed.

In arranging the compacter elements C to effectively cover the area to be cleared, it is desirable to, at the sam time, space the elements far enough apart to confine the effects of the explosion of a mine detonated by one element to that particular element' The use of alternate short and long actuating arms 21 and 28 achieves this result Without sacrificing distance. The interpositioning of the elements on the shorter arms 27 increases the spacing of the elements on the longer arms 28, and, hence, protects the outer row of elements without increasing the spacing of the points of impact in the overall pattern.

As shown in dotted lines in Figure 4, the eccentrics of each set of three are spaced apart about the periphery of the shaft 2|. In this way, rotation of the shaft will produce a series of impacts in one, two, three order, assuming that two mine explosions will not occur simultaneously within any given group of three compacter units. Th next group of three would be similarly spaced within the group, but preferably the group as a whole would be somewhat displaced from the previous group to insure that similar elements of each group did not impact at the same tim with the possibility of simultaneous explosions in similar positions in each group. Obviously, simultaneous explosions would greatly multiply the chances of damaging the apparatus. In the particular example shown, each group of elements is offset twenty degrees with relation to the group preceding it, and each element within a group is offset 120 with relation to the other two elements in the group. In this way, an impact order for a group of nine units may be set up as follows: 1, 4, 7, 2, 5, 8, 3, 6, 9. Figures 5 and 6 show diagrammatically the path followed by a given cornpacter unit as it moves through its cycle of operation. As will be seen from Figure 6, the dotted line path taken by the foot of an element with relation to the ground is not unlike the path followed by the front hoof of a trotting horse in that it strikes the ground and moves up and forward without sliding movement in relation to the ground. This is important in obtainin sustained pressure at the point of impact;

As has been previously mentioned, cables 34 have been provided as a means of adjusting the inclination of the housing. 33 and since the arms are pivoted therein, it will be apparent that the position of the compacter feet with relation to the ground may also be regulated thereby. An electrically operated winch, such as that shown in Figure 12, provides one convenient means of controlling the length of the cable. In actual practice, it wil1 be found that on normally hard terrain the major portion of the unbalanced weight of the compacter assemblies will b borne by the elements in contact with the ground at any given time. Hence the cable may usually be left slack and the compacter feet will walk forward enabling the device to automatically respond to variations in the contour of the earth in its path. When the device is to be moved from place to place without contacting the ground, the cables S l are wound to elevate the compacter elements above the ground.

As shown in Figures 2 and 4, the cables 34 are attached to the housings 33 and then pass over the guide pulleys 36. The cables may be wound and unwound by any suitable mechanism, either mechanical or electrical. As an example of one form of mechanism which may be provided, there is shown in Figure 12 an electric winch. In Figure 12, the cable 34 is wound on a drum 3? fixed to shaft 38 mounted in bearings 39. A'gear H is also fixed to shaft 38 and meshes with worm- 42 on shaft 43. Shaft 43 journaled at 45 is driven by an electric motor 35. The directionof rotation of the drum 3'! is determined by the direction of rotation of motor 55. Any suitable reversing and control mechanism may be provided for the motor, but since such controls are well known, they are omitted from the illustration. Obviously, the control used should provide simplicity and ease of operation with reliability.

Although the device has been shown as split up into two groups, each of which may be com trolled individually with regard to height above th ground, it is obvious that this breakdown may :be carried even farther with consequent improvement in flexibility and ability to follow rough contours. The two groups together are shown as having substantially the same width as that of the actuating vehicle, but further increases in the number of units not only assists in reducingv the probability of damage to the units from exploding mines, but may afiord greater compacting range and flexibility. When a greater number of groups is used, they may, and preferably do, extend laterally beyond the propelling vehicle so as to insure adequate width of the compacted area when traveling around curves or making sharp turns. Any permissible increase in width of the compacted area reduces the number of passes required and affords more economical use of the propelling vehicle.

As indicated above, it is possible to so design the apparatus that the explosive impact of an exploding mine places substantially no stress upon the compacter element, as the kinetic energy of the blast is balanced by the kinetic energy of the compacter element as it is driven downwardly. Therefore, with this balanced operation, the use of energy absorbing devices in conjunction with the compacter elements is not theoretically necessary to protect the mechanism against the destructive impact of a mine blast. Where, however, the'forces are not strictly-balanced, such devices are useful,- and they are always usefulinrelieving the mechanism of stresseszimparted to it by the pounding shocks which themechanism receives as the apparatus operates over a hardsurface.

In describingthe efiect produced upon a compacter element, especially when subjected to the blast ofan explodingmine, each of the comp-acter.-elements C may be compared with a-gun in reverse. By thisit is meant that the compacter element which, by impact, causes the explosion of the mine will be propelled in a generally vertical direction .awa from the-explosion. The body of the compacter may be made in the generalform of a cylinder in whichv th footof the element can move-against. the resistance of suitable energy absorbingmeans generally similar to a cannon-recoil mechanism to receive and dissipatetheshock, while means in general. similar to a .recuperator mechanismreturn the compacter foot .to its normal operating position. ,Pr'eferably, the compacter. elements and the forwardly extending arms 21 and,28 will be of streamlined formto reduce. the amount of .force which will be taken upfrom the blast, and a staggered arrangement of the compacter units will be employed to permit the escape of the gases of the explosion. with .a minimum of obstruction.

The energy absorbing means employed may assume various forms andmay. be mechanical, pneumatic or hydraulic, or combinations of these, but. it isat present preferred to use a combinationof hydraulic and spring means in which the hydraulic means absorbs the recoil and the spring acts as a recuperator. Considered ,from the standpoint of absorbing mechanical shock as the device operates over the ground both the spring and the hydraulic mechanism act concurrently. The smaller shocks are substantiall absorbed by the spring, whereas shocks suflicient to stress and deform the spring cause movement of the hydraulic piston against the opposition of the hydraulic fluid. This. action will be set forth in the description of specific embodiments which follows.

A preferred form of compacter incorporating a combination spring and hydraulic energy absorbing means is shown in Figure 7. In this embodiment emphasis is placed upon the design andlocation of vulnerable parts so as to protect themagainst damage caused by the blast of exploding mines.

In Figure '7, the foot lfi'of the compacter element composed of mechanically resistant and erosion j resistant steel, such as hardened armor plate, increases in diameter upwardly until it terminates in a tapered body 41 and a guard sleeve 48. The foot and the body form a smooth taper which offers a minimum opposition to an explosive blast, and the cylindrical guard sleeve 48. encloses andshields the spring and hydraulic mechanism both from mechanical damage and from the erosive effects of burned gases.

Body d! is countersunk to receive the threaded end iSi'ofa piston rod 5|, and again at 52 to form a seat for the lower end of a spring 53 surrounding the piston rod 5 I. The spring 53 reacts between the countersink and a guide 54 movable within the sleeve 48. The guide 54 is composed or upper and lower sectionsthreaded together at 55, and the upper section not only carries an hydraulic cylinder 55- threaded to itat 51, but is countersunk to receive a piston 58 formed integrally with piston rod 5|. The chamber for fluid isformed between the pistonrod 5| above .piston combinations of the two.

58 and the inner wall of cylinder 56. This wall is. contoured, parabolically as shown, to provide predetermined resistance to upward movement of the piston rod as the hydraulic fluid is forced through the orifice formed by piston 58 and the inner wall of cylinder 56 during upward movement of the piston. The cylinder 56 embraces the reduced upper end of piston rod and the joint is sealed by a packing 59, held in a ring 6| threaded into the recessed upper end of cylinder 56. attached to the element by a bracket 62 welded or otherwise secured to the cylinder 56. The guard sleeve 48 may be slotted at 63 to permit free movement of the foot and attached parts without striking the bracket.

It will be apparent that in the structure shown the spring 53, aided by gravity, biases the piston rod 5| and attached parts including foot 46 downwardly to the extreme position shown, while upward movement of the piston rod and foot. is opposed not only by the spring, but also by thehydraulic fluid. The parts are preferably so arranged in practice that the overall resistance opposed to the upward movement of the foot 46 by 10 The supporting and actuating arm may be the spring, the hydraulic mechanism and the impacts and smooths out the reactions which' are transmitted to the compacter supporting means.

The means, is therefore, efiective to reduce wear and tear on the apparatus occasioned either by mine blasts or by mechanical impact, or by Furthermore, the expensive and vulnerable parts in the mechanism are protected by guard sleeve 48 against metal fragments and explosion gases. This not only prolongs the usefulness of the mechanism, but avoids welding of the parts together by the heat of explosions, as may occur when the exposed parts are in several pieces. Consequently, the foot 46 and parts integrally attached to it can always be removed and replaced when the foot has been abraded or eroded to a point where it is no longer useful. In this way, the most vulnerable part of the compacter, namely the foot, can be replaced at intervals to not only reduce materially the weight of spare parts to be carried, but also to reduce the frequency and extent of servicing required.

Figures 8 and 9 show a preferred form of hydro-pneumatic absorbing means in which a flexible metal bellows containing air or other gas is disposed in a chamber laterally of the hydraulic piston chamber, and it provides the advantage of a double end support for the piston, of small displacement of liquid, and also of utilizin a simple and conventional type of metal bellows.

In Figure 8 all parts of the compacter except the absorbing mechanism are omitted for'simplification. It will be understood that any type of foot previously described may be utilized. The piston rod 64 in this figure has its lower end guided in a fitting 65 secured to barrel 66. This fitting is threaded into or otherwise secured to the barrel 66 and serves not only to guide the piston rod 64, but also to form the bottom of the hydraulic cylinder 61 and of the bellows chamber 68. The two chambers are filled with hydraulic fluid but are separated by a, wall 69 terminating below the cover plate H for the two chambers so as to provide a liquid flow path I2.

The cover plate ll contains a stufiing box 13 which seals the upper reduced end of the'piston rod 64 with respect to the fluid chamber.

The piston rod 64 carries a piston 74 and is of much reduced diameter above the piston. The bellows chamber 68 contains a Sylphon bellows 75 supported from the cover plate 1| and having a charging fitting 16. The Sylphon is exposed to pressure by liquid fed laterally from the piston chamber into the Sylphon chamber and, therefore, serves not only to oppose upward movement of piston 14, but tends to restore the piston M to the position shown in the drawing. The charge of air or other gas in the bellows may be varied to secure widely varying opposing pressures. The diiTerence in diameter of the piston rod above and below the piston 14 makes it possible to utilize a relatively small. bellows. The amount of liquid transferred to the bellows chamber is determined by the diiference in these rod diameters, hence the liquid volume to absorb a given pressure in the bellows is much less than would be the case if the rod were of the same diameter below the piston that it is above it.

Figure 10 illustrates still another form of compacter element embodying hydro-pneumatic energy absorbing means. In this form the rod 7,! extends through a stufiing box 18 and terminates below in a foot similar to that of'Figure 7. The piston rod ll carries a piston l9 movable in a cylinder 8 The cylinder is connected to an actuating arm 82, through a rubber shock absorbing sleeve 83. Communicating with and carried above the cylinder 8| is an hydraulic chamber 84 containing fluid 85 and a metal bellows 86 mounted between the upper face of chamber 84 and the cover plate 81. The bellows has a charging fitting 88. The opening at the entrance to the bottom of the chamber carries an annular orifice ring 89, through which moves piston rod 11 having a contoured surface 9| to exert an orifice effect in conjunction with ring 89 and control the flow of liquid 'from the space below the ring to that above it as the piston rod and thepiston 79 carried by it moves upwardly into the cylinder 84. Placing the contoured surface on the exterior of the piston rod instead of on the inside of the cylinder as in Figure 8 simplifies machining operations, permits use of an elongated piston 19 with a longer bearing surface and permits a longer stroke of the piston than is practicable with the arrangements of Figure 8. l

The arrangement shown in Figure 11 utilizes a simple pneumatic energy absorbing means without the use of hydraulic'fiuid or springs. In this figure, 92 designates the foot of the compacter having an integral grooved piston-93 carrying packings 96. The piston with its packings is movable in the cylinder 95 supported in a rubber mount 96 onthe end of actuating arm 91. The cylinder 95, closed at the top, contains openings 98 to restrict the outflow of air as the piston moves upwardly. Gravity is relied-0n to restore the piston to the bottom of its stroke.

Arm 91 may be actuated by eccentric 99 and about fulcrum |9| carried by the arm and movaable in a resiliently supported bushing I62 having a suspension spring I03 carried by mount I94 and having arubber cushion I95 beneath it and carried by the mount. This arrangement is provided to show the feasibility of using a resiliently mounted fulcrum and a simple form of absorbing mechanism.

It will be clear from the above description that numerous variations in the structure may be in ice ancLis, attached: toiagpropelling vessel .the

adjusting meansrpermits regulation of the'height of theqdevice as desired andthis may be dependent upon the thickness of the .ice to be broken. When ice is beingf-brokenon a body of water having current, the ,devicewill be directed up.- streamso that fragments oficebroken ofi will becarried downstreamby the current, thus making the device self-clearing.

The adjusting .means. isv of particular utility whenithe apparatus is vemploye'd'in mine ,"fleld clearing. i It may include a counterspringto support a partof the cantilever weight of the device, thus relieving the stress on the cable "34. and. assisting in avoiding excessive. penetration of the elements into the earth. traversing .'muddyterrain,;the feet-willbe elevated to control the Ldepthto which they are :driven, and'to prevent themirom being ffbo ged down and rendered ineffective. ".By. suitable adiustment of this character the device can be made to; pass through deep mud-whilestillppenetratingto; a depth sufficient to insure detonation of any mines which could be present. The device has-particular utility in clearing mines. from rocky terrain: since the feet by suitable reg-ulation of the adjuster will enter 'depressions'between rocks and cup-like depressions which would be bridged and passed over bymechanism including l rge" diameter rollers.

.In minejfieldsowing it -is-customary to'rutilize 45 barbed wire entanglements'surrounding-the field in" order torender minesclearing more difficult and'to impede progress of the -pursuing army.

This device is capable of passing through-barbed wireas an incident to its operation'while' still-exploding all mines" and 'avoidingentanglement" of the exploding elements. Instead ofdriving-the device forward continuously as in normal -opera tion, the device may be moved intermittently and stoppedat short intervals while the'feetareliited above the wire by'thecableand then dropped by releasing the cable to pass through the entangled wire-andto explode any mines planted under the wire. In'this' way, the device operates vertically into the entanglement and no attempt is; made to push 'theelements horizontally through the wire. 'the-exploderelements pass over the" wire direct- Consequently, the mines-are-exploded and ing it underneath the-propelling vehicle where it iscrushed.

While the compacter-element "structure shown in Figure 7 has been" indicated-"asthe preferred one,: it is pdesired to .pointout the possibilities 'of using "the energy or shock *absorbinggelements 'shown in Figures 811'-in*relations T'OthBl' than those shown. 7 'So" faras I am-aware; it has never before been proposed to employ a ":Sylphon' bellows in combination with hydraulidmechanism "as a recuperator. Such 1 an arrangement, particularly where i the bellows 'is mounted in an oil" ".When .the device is bathQhasa highly practical aspect. So long as they possible distortion of the bellows is maintained within the'limits of the device, it is capable of efiective use for long. periods. .The usual "6 troubles .caused by .emulsification of the oil are non-existent since the air. is confined within the bellows. and changes in the angular position of the oil chamber 'do not cause mixing of air with theoil.

TheSylphon bellows,.by variation in thepressure of the. charging .gas within it, is flexible enough topermit a Wide range of adjustment of its recuperator function, that is, the higher the pressureof thecharging gas, the more resistance it presents to deforming forces, and conversely, the..low,er,.the pressure of the charging .gas, the lower. the, resistance it opposes to deformation. 'Thebellowswhen mounted in an oil chamber, is protected against atmospheric oxidation and *Zomechanical injury, and presents none of the problems'that are characteristic of rubber bags whichhave been used before forthis purpose. ThefSylphon'bellows also offers th advantageof absorbing great amounts of energy through a short stroke of .the mechanism, although when combinedwith hydraulic absorption, almost any lengthofstroke may be obtained, with appropriate variations of the opposition obtained at particular points in the stroke.

.In this description it has been pointed out how .the energy absorbing action of the. hydraulic fluid maybe adjusted to suit particular conditions,

thatis, by making either the inside wall of the cylinder parabolic'in cross section as in Figures 7-and'8, or the piston rod surface parabolic and passing througha fixed orifice as in Figure 10. Obviously,.the. orifice size may be varied to suit conditions, or it may have such a low retarding value that the compression of the bellows may 40 servesubstantiallyby itself as the energy. absorbing means. The bellows may be charged either, with air or with any inert gas, such as nitrogen orLthelike, where particular characteristics -.are"de'sired. Variation ,Of] the response may then ".be accomplished eitherbychanging the pressure of. the jcharginggas or by ,varyingthe cross sec- .tional area of the sylphon or. of. the hydraulic piston .or by anyjcombination ..of these variables. "Obviou'sly,jthe sylphon' bGHOWSrhYdIBIllU-C combination, may be useful in various relations where energy or "shock absorbing action is'desired, and where'flexibility of design to suit various conditions, isdesired. .The above'description is to be construed -with these variations in mind and without limitation to the particular embodiments illustrated.

Having thus described the invention, what. is :claimed is:

"1.1The combination with apropelling vehicle 0 of a'compacting device comprising a frame, a

chambered body mounted upon said frame, a ground engaging foot of 'wear resistant'material .associated'with'said chambered body and telescoping'therewith, and combined hydraulic and '65 :pneumatic energy absorbing means mounted ..in

" said body and arranged to oppose relative"move ;ment between said foot and said body.

32.1.Thecombination witha propelling vehicle "of acompacting device comprising a'frame, a

- chambered body mounted upon said frame, a

ground engaging footof wear resistant 'material associated with said chambered bodyand telescoping therewith, and energy absorbing. means mounted in said .body and'arranged to oppose *movement "of" said foot -into said body, said absorbing means comprising hydraulic recoil means having a gas filled Sylphon bellows recuperator mounted therein.

3. The combination with a propelling vehicle of a compacting device comprising a frame havin a plurality of striking elements mounted thereon, each of said striking elements comprising a cylinder containing hydraulic liquid; a piston movable in said cylinder and having rodlike extensions passing through the cylinder ends; orifice means formed in said cylinder for restrictin the flow of liquid from one side of the piston to the other; and a closed metal bellows disposed in the liquid and adapted to be compressed by the liquid displaced by said piston during its movement in one direction in said cylinder.

4. The combination with a propelling vehicle of a compacting device comprising a frame having a plurality of striking elements mounted thereon, each of said striking elements comprising an hydraulic chamber having liquid therein; a piston movable in said chamber and serving to displace liquid from one portion of said chamber to another at a controlled rate; and a flexible metal bellows mounted in said chamber and acting to assist the liquid in opposing movement of the piston in one direction and tending to restore the piston to its initial position.

5. The combination with a propelling vehicle of a compacting device comprising a frame having a plurality of strikin elements mounted thereon, each of said striking elements comprising a piston rod movable in a liquid chamber; a piston carried by said rod between its ends and defining rod sections of two different diameters; a second chamber communicating with the liquid chamber on the side of the piston having the smaller rod diameter; and a closed flexible metal bellows disposed in the second chamber in a position to be compressed by liquid displaced from the liquid chamber by said piston upon recoil and serving to recuperate said piston to its initial position.

6. Th combination with a propelling vehicle of a compacting device comprising a frame, a chambered body mounted upon said frame, a ground engaging foot of Wear resistant material associated with said chambered body and telescoping therewith, and energy absorbing means mounted in said body and arranged to oppose movement of said foot into said body, said energy absorbing means including hydraulic fluid recoil absorbing means combined with spring recuperator means.

ALLISON R. WILLIAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 494,909 Wallis Apr 4, 1893 1,174,803 Bathrick May 7, 1916 1,654,014 Proctor et a1 Dec. 27, 1927 1,841,802 Gettelman Jan. 19, 1932 1,391,222 Cornett Dec. 20, 1932 1,893,596 Perkins Jan. 10, 1933 1,936,788 Hardy Nov. 28, 1933 2,029,363 Downie Feb. 4, 1936 2,136,315 Pettit Nov. 8, 1938 2,146,101 Weber Feb, 7, 1939 2,242,808 Austin May 20, 1941 2,334,708 Joy Nov, 23, 1943 2,372,023 Schnell Mar. 20, 1945 

